Multiple disc type filter and disc construction useful therein

ABSTRACT

A disc-type filter including a housing having an inlet connectable to an upstream pipe, and an outlet connectable to a downstream pipe; and a stack of discs disposed within the housing for separating solid particles from a fluid flowing between the discs from the upstream side of the stack to the downstream side thereof; characterized in that the stack includes: 
     a plurality of cooperating filter elements defining a plurality of paired co-operating filter surfaces, including a first surface having a large surface area and a second surface contacting only a portion of the large surface area of the first surface and leaving a portion of the large surface area on the upstream side of the stack not contacted thereby, at least one of said first and second surfaces being formed with grooves at the areas at which the first and second surfaces contact, thereby to form: 
     a) compartments on the upstream side of the stack for accumulation of solid particles; and 
     b) edge filtering passageways extending along the grooves in contact with the second surface, which passageways define the minimum size of particles separated by the filter and extend from the compartments to the downstream side of the stack, and wherein the second surface is formed with serrated edge surfaces defining the compartments on the upstream side of the stack, thereby increasing the length along which edge filtering passageways are defined.

This is a continuation of Ser. No. 07/167,999, filed 3/14/88, now U.S.Pat. No. 4,880,537 which was a continuation of Ser. No. 06/850146, filed4/10/86, now U.S. Pat. No. 4,744,901.

FIELD OF THE INVENTION

The present invention relates to multiple-disc filters useful infiltering particles from water and in many other applications.

BACKGROUND OF THE INVENTION

Multiple-disc type filters are known generally and include a housing inwhich is disposed a filter body in the form of a stack of like,centrally-apertured, filter discs of substantially uniform thicknessalong their widths. The individual discs have grooved side facesdefining filtering channels between the adjacent discs in the stack.

Multiple-disc type filters have a number of advantages over other knowntypes of filters, for example the cylindrical screen type filter, inthat the multiple-disc filter has a relatively large capacity forremoving and retaining dirt particles, since these may be retainedbetween the side faces of the discs in addition to being retained on theupstream surface of the filter. The multiple disc filter is alsocharacterized as being relatively easy to clean and resistant to ruptureand is operative even at relatively low pressures.

In my copending U.S. patent application Ser. No. 709,372, filed on Mar.7, 1985 now U.S. Pat. No. 4,683,060 dated July 28, 1987 and claimingpriority from Israel Patent Application No. 73923 there is described adisc-type filter including a housing having an inlet connectable to anupstream pipe, and an outlet connectable to a downstream pipe; and astack of discs disposed within the housing for separating solidparticles from a fluid flowing between the discs from the upstream sideof the stack to the downstream side thereof; characterized in that thestack includes:

a plurality of cooperating filter elements defining a plurality ofpaired co-operating filter surfaces, including a first surface having alarge surface area and a second surface contacting only a portion of thelarge surface area of the first surface and leaving a portion of thelarge surface area on the upstream side of the stack not contactedthereby, at least one of said first and second surface being formed withgrooves at the areas at which the first and second surfaces contact,thereby to form:

a) compartments on the upstream side of the stack for accumulation ofsolid particles; and

b) edge filtering passageways extending along the grooves in contactwith the second surface, which passageways define the minimum size ofparticles separated by the filter and extend from the compartments tothe downstream side of the stack.

SUMMARY OF THE INVENTION

The present invention seeks to provide an improved disc-type filter ofthe type described generally in my aforesaid copending U.S. patentapplication.

There is thus provided in accordance with a preferred embodiment of thepresent invention, a disc-type filter including a housing having aninlet connectable to an upstream pipe, and an outlet connectable to adownstream pipe; and a stack of discs disposed within the housing forseparating solid particles from a fluid flowing between the discs fromthe upstream side of the stack to the downstream side thereof;characterized in that the stack includes:

a plurality of cooperating filter elements defining a plurality ofpaired co-operating filter surfaces, including a first surface having alarge surface area and a second surface contacting only a portion of thelarge surface area of the first surface and leaving a portion of thelarge surface area on the upstream side of the stack not contactedthereby, at least one of said first and second surfaces being formedwith grooves at the areas at which the first and second surfacescontact, thereby to form:

a) compartments on the upstream side of the stack for accumulation ofsolid particles; and

b) edge filtering passageways extending along the grooves in contactwith the second surface, which passageways define the minimum size ofparticles separated by the filter and extend from the compartments tothe downstream side of the stack, and wherein the second surface isformed with serrated edge surfaces defining the compartments on theupstream edge of the stack, thereby increasing the length along whichedge filtering passageways are defined.

Further in accordance with a preferred embodiment of the presentinvention means are provided for maintaining the plurality ofco-operating filter elements in predetermined desired relative azimuthalorientation with respect to the longitudinal axis of the stack.

Additionally in accordance with an embodiment of the present inventionthere is provided a disc-type filter including a housing having an inletconnectable to an upstream pipe, and an outlet connectable to adownstream pipe; and a stack of discs disposed within the housing forseparating solid particles from a fluid flowing between the discs fromthe upstream side of the stack to the downstream side thereof;characterized in that the stack includes apparatus for maintaining thestack of discs in predetermined desired relative azimuthal orientationwith respect to the longitudinal axis of the stack.

Further in accordance with an embodiment of the present invention, thesecond surface contacts the first surface such that a portion of thelarge surface area of the first surface at the downstream side of thestack is not contacted by the second surface.

Additionally in accordance with an embodiment of the invention, both thefirst and second surfaces contain grooves at the areas at which thefirst and second surfaces contact.

In accordance with one embodiment of the invention, the plurality offilter elements includes a first plurality of filter discs interspersedwith a second plurality of spacer discs.

In accordance with an alternative embodiment of the present inventionthe plurality of filter elements includes a plurality of filter discshaving the first surface form on one face thereof and the second surfaceformed on an opposite face thereof.

Additionally in accordance with an embodiment of the invention thesecond surface where it contacts said first surface is flat.

Further in accordance with an embodiment of the invention the area ofthe first surface which is not contacted by the second surface isgreater than the area of the first surface which is contacted by thesecond surface.

Additionally in accordance with one embodiment of the present invention,the first surface has grooves extending in a generally radial directionand the second surface defines upstream edges which are mostlycircumferential in orientation.

In accordance with an alternative embodiment of the invention the firstsurface has grooves extending in a generally circumferential directionand the second surface defines upstream edges which are mostly radial inorientation.

Further in accordance with an embodiment of the invention, the secondsurface defines edges in a sinuous configuration.

According to an alternative embodiment of the present invention, thesecond surface defines accumulator grooves which are substantially widerthan the grooves of the first surface, the grooves of the first surfacebeing contacted by the crests of the accumulator grooves and beingspaced from the valleys of the accumulator grooves.

According to one embodiment of the invention, the accumulator groovesextend generally in the radial direction and the grooves in the firstsurface also extend generally in the radial direction but at a differentangle than the accumulator grooves.

According to an alternative embodiment of the invention, the accumulatorgrooves extend generally in the radial direction and the grooves in thefirst surface extend in the circumferential direction.

Further in accordance with an embodiment of the present invention, thegrooves in said first surface are tapered, thereby to define a fluidflow passageway in the narrowed region thereof even when the remainderthereof is filled with particles.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be understood and appreciated more fully from thefollowing detailed description, taken in conjunction with the drawingsin which:

FIG. 1 is a longitudinal sectional view illustrating one form of filterconstructed in accordance with the present invention;

FIG. 2a is an enlarged fragmentary view illustrating the main elementsof the filter stack in the filter of FIG. 1 according to one embodimentof the invention;

FIG. 2b is a sectional view along lines b--b of FIG. 2a;

FIG. 2c is an enlarged view along lines c--c of FIG. 2a;

FIGS. 3 and 4 illustrate two modifications in the filter of FIG. 1;

FIGS. 5a and 5b are views corresponding to FIGS. a and 2b butillustrating a further modification in the filter of FIG. 1;

FIGS. 6-10, 10a and 11 illustrate filter variations in the structure ofthe filter of FIG. 1;

FIG. 12 illustrates a further construction which may be used in thefilter of FIG. 1;

FIG. 12a is a sectional view along lines a--a of FIG. 12;

FIGS. 12b and 12c illustrate the construction of each filter disc andeach separator disc in the filter of FIG. 12;

FIGS. 13, 13a, 13b and 13c are views corresponding to FIGS. 12, 12a, 12band 12c, of a further modification in the construction of the filter;

FIG. 14 is a sectional illustration of a non in-line filter which mayemploy filter elements in accordance with the present invention;

FIG. 15 is an illustration of a portion of a filter disc having a firstsurface defining grooves and a second surface which acts as a spacer;

FIG. 16 is an illustration of two stacked filter discs of the typeillustrated in FIG. 15;

FIG. 17 is an illustration of two stacked filter discs of the generaltype illustrated in FIG. 15 but having grooved second surfaces;

FIG. 18 is an illustration of a filter disc having a first surfacedefining a slanted groove pattern and a second surface defining anaccumulator groove pattern having an opposite slant;

FIG. 19 is an illustration of two stacked filter discs of the generaltype illustrated in FIG. 18;

FIGS. 20 and 21 are respective illustrations of a single filter disc andthree stacked filter discs of the same configuration, each disc bearingfirst and second surfaces having the respective groove patterns whichappear on separate discs in the embodiment illustrated in FIG. 12;

FIGS. 22, 23 and 24 are respective illustrations of a single filter discand two stacked filter discs of the same configuration, each discbearing filter and second surfaces having the respective groove patternswhich appear on separate discs in the embodiment illustrated in FIG. 13;

FIGS. 25, 26 and 27 are respective pictorial illustrations of both sidesand a sectional illustration of two stacked filter discs of the sameconfiguration, each disc bearing first and second surfaces havingrespective groove patterns;

FIGS. 28 and 29 are respectively a pictorial illustration of a filterdisc having another configuration and a partially cut away pictorialillustration of a stack of such filter discs;

FIG. 30 is a sectional illustration of the filter disc of FIG. 28 takenalong the lines A--A in FIG. 28; p FIGS. 31 and 32 are respectively apictorial illustration of a filter disc having yet another configurationand a partially cut away pictorial illustration of a stack of suchfilter discs;

FIGS. 33 and 34 are respectively a pictorial illustration of a filterdisc having still another configuration and a partially cut awaypictorial illustration of a stack of such filter discs;

FIG. 35 is a pictorial illustration of a stack of filter discs havingstill another configuration;

FIG. 36 is an illustration of a second surface of a filter disc having aplurality of upstream facing edges in generally circumferentialorientation;

FIG. 37 is an illustration of a second surface of a filter elementhaving serrated edges facing in the upstream direction and means forenabling a stack of such filter elements to be retained in apredetermined desired azimuthal orientation; and

FIG. 38 is a pictorial illustration of a stack of filter elements of thetype shown in FIG. 37 held together in a desired azimuthal orientation.

DETAILED DESCRIPTION OF THE DRAWINGS

The filter illustrated in FIG. 1 is of the in-line type including ahousing 2 comprising an inlet 4 connectable to the upstream pipe and anoutlet 6 connectable to the downstream pipe. Disposed within housing 2is a filter body 8. The inlet includes a deflector 10 causing theinletted water to flow through inlet openings 12 to an annular chamber14 around filter body 8, radially inwardly through the filter body 8,and then through outlet openings 16 to the housing outlet 6.

Filter body is of the multiple-disc-type, including a plurality offilter discs secured in a stack between end rings 18 and 19. Housing 2is made of a plurality of sections which may be opened in order toprovide access into the interior of the housing, and ring 19 isthreadedly applied to one section to permit the filter discs of filterbody 8 to be disassembled for purposes of cleaning or repair.

Such filters are well known and in extensive use today and thereforefurther details with respect to the construction, operation or cleaningof such filters are not necessary here.

As in the conventional multiple-disc-filter in use today, filter body 8comprises a plurality of filter discs 20 (FIGS. 2a, 2b) of annularconfiguration and formed on both side faces with a plurality of grooves21 extending generally in the radial direction; the term "generallyradially" is intended to include grooves formed tangential to theopening through the filter disc, which grooved formation is alsosometimes used.

In the filter illustrated in FIGS. 1, 2a and 2b, the filter body 8further includes a plurality of spacer members 22, there being one suchmember interposed between each pair of adjacent filter discs 20. Thespacer members are of annular configuration and are disposed to contactonly the inner portion of the grooved faces of the filter discs, thisbeing the portion of the grooved faces on the downstream side of thestack; thus, the annular spacer members 22 do not contact the outerportion of the grooved faces of the filter discs 20, which grooved facesare on the upstream side of the filter stack. The provision of spacermembers 22 to cover only a portion of the grooved faces of the filterdiscs 20 on the downstream side of the discs produces the followingeffects:

(a) The spacer members form compartments 24, as shown in FIG. 2b, on theupstream side of the stack for the accumulation of solid particlesremoved from the fluid inletted into the housing; these solid particlestend to settle within the grooves 21a, 21b (FIG. 2c) of the filter discs20, because there is a fluid flow through these grooves as will bedescribed more particularly below.

(b) Spacer members 22 also form edge-filtering passageways along theupstream edges (outer edges) of the spacer members in contact with thegrooved faces of the filter discs; these passageways actually define thesize of the solid particles separated by the filter body 8.

(c) The provision of spacer members 22 produce further filteringpassageways in the compartments 24, these latter passageways includingthe spaces between the particles settling within the grooves 20a, 20b ofthe filter discs, and extending through these grooves to the downstreamside of the stack.

It will thus be seen that there is fluid flow not only through thegrooves 21a, 21b covered by the upstream (outer) edge of the spacermembers 22, but also through the portion of the grooves not covered bythe spacer members. Because of the latter fluid flow, the particles willtend to settle within the portions of the grooves 21a, 21b not coveredby the spacer member 22. This arrangement thus provides a large surfacearea of the filter discs to receive and retain the separated particles,and thereby distributes the separated particles over a larger surfacearea than, for example, in the conventional arrangement wherein theseparate particles accumulate primarily at edge-filtering passageways.Accordingly, the described arrangement enables very substantialquantities of solid particles to be separated and retained within thefilter before cleaning is required.

FIG. 3 illustrates a variation wherein the spacer members 32 are also ofannular configuration but each includes a plurality of radial extensions34 extending in the upstream direction to overlie the filter discs 30.These radial extensions 34 are provided primarily for mechanicalpurposes, to mechanically support the outer edges of the filter discs30.

FIG. 4 illustrates another variation, wherein the filter discs 40 areformed along their outer (upstream) edges, with a plurality ofprojections 44 for mechanically supporting the outer edges of the discssince their inner edges are spaced from each other by the annular spacermembers 42 corresponding to members 22 in FIGS. 2a-2c.

FIGS. 5a and 5b illustrate another variation wherein the annular spacermembers 52 are interposed between the grooved filter discs 50 alongtheir outer edges. This arrangement would be used when the fluid flow isin the radial outward direction, rather than in the radial inwarddirection, such that the uncovered portions of the grooved faces of thefilter discs 50 would be on the upstream side of the stack, as describedabove.

FIGS. 6-8 illustrate three arrangements wherein the annular spacermembers, therein designated 62, 72 and 82, respectively, are of sinuousshape and include a plurality of curves or turns. In such shapes, themajor portions of the spacer members extend generally in the radialdirection with respect to the grooved filter discs 60, 70 and 80,respectively, and therefore the grooves in these filter discs extend inthe circumferential direction rather than in the radial direction.Forming the spacer members 62, 72, 82 of sinuous configurationsubstantially increases the edge-filtering passageways defined by theirupstream edges. In FIG. 6 and 7, the spacer members 62, 72, uncoverlarger surfaces of the disc grooved faces along the outer sides of thediscs, and therefore the outer sides would be the upstream sides of thefilter; i.e. the fluid would flow in the radially inward directionthrough the filter stack. In FIG. 8, however, the spacer members 82uncover larger grooved surfaces at the inner sides of the filter discs80, and therefore the inner sides would be the upstream sides; that is,the fluid would flow in the radially outward direction.

FIG. 9 illustrates an arrangement similar to that of FIG. 6, butincluding webs 94 interconnecting the turns of the spacer members 92 toprovide mechanical reinforcement of the latter members. Theinterconnecting webs 94, however, are spaced from the outer face of therespective filter disc 90 so as not to contact the grooved surfaces ofthe disc covered by the webs. Thus, the webs do not interfere with thefunction of the spacer member to define compartments (corresponding tocompartments 24, FIG. 2b) for the accumulation of dirt particles withinthe grooves of the filter discs. It will be appreciated that since thegrooves within the filter disc 60, 70, 80, are in the circumferentialdirection, the fluid flow will be in the radial direction on oppositesides of the spacer members but will be in the circumferential directionacross the spacer members.

FIG. 10 illustrates another arrangement including spacer members 102 ofsinuous configuration and providing large surface areas of the grooveddiscs 100 at the upstream side (outer side) of the filter discs notcovered by the spacer members. FIG. 10a illustrates an arrangementsimilar to that of FIG. 10 but including webs 104 interconnecting theturns of the spacer members 102 to mechanically rigidify the spacermembers.

FIG. 11 illustrates a still further arrangement in which the filterdiscs 110 have radially extending grooves, and the spacer members 112have a radially extending section 112a, and two circumferentiallyextending sections 112b, 112c. This arrangement is to provide a longedge-filtering passageway, defined by the upstream edge of the spacermembers in contact with the grooved faces of the filter discs. It willbe appreciated that in the arrangement illustrated in FIG. 11, the outerside of the filter disc 110 constitutes the upstream side of the stack,and therefore the fluid would flow in the radially inward direction.

FIGS. 12 and 12a-12c illustrate a still further variation, in which thespacer members 122 are formed with grooved faces, as shown at 122a, butthese grooves are both substantially wider and deeper than the grooves120a of the filter discs 120. As shown particularly in FIG. 12a, theinner portion 122b of the spacer members 122 is not grooved, but ratheris flat and therefore contacts the grooves 120a of the filter discs.However, the outer grooved portion 122a of the spacer members, whichlatter portion constitutes the major surface area of the spacer members,are in contact only at their crests with groove 120a of filter discs120, the valleys of the groove 122a being spaced from grooves 120a ofthe filter discs. Accordingly, the arrangement illustrated in FIGS. 12and 12a-12c still define compartments, corresponding to compartments 24in FIG. 2b, for the accumulation of solid particles, and also providethe large surface area filtering passageways for the flow of the fluidthrough the portions of the grooves 120a within these compartments tothe downstream side of the spacer members.

It will be seen that, in the arrangement illustrated in FIGS. 12 and12a-12c, the grooves 120a in the filter discs 120 extend in the radialdirection, and the larger and deeper grooves 122a formed in the spacermembers 122 also extend generally in the radial direction. However, thelatter grooves are at a different angle than grooves 120a in the filterdiscs 120, so that the crests of grooves 122a will engage the crests ofgrooves 120a, and will not penetrate to the valleys within the lattergrooves.

FIGS. 13 and 13a-13c illustrate an arrangement similar to that of FIG.12, except that the filter discs, therein designated 130, are formedwith circumferentially extending grooves, rather than radially extendinggrooves. The larger and deeper grooves 132a formed in the spacer members132 extend in the radial direction, as in FIG. 12. In addition, thegrooves 132a in FIG. 13 are of the V-shaped section, whereas the grooves122a in FIG. 12 are of U-shape.

Reference is now made to FIG. 14, which shows an alternative filterstructure, here termed a non in-line filler in which the filter discs ofthe present invention may be employed. Thus, it may be appreciated thatthe filter discs of the present invention may be employed in filters ofthe types illustrated in FIG. 1 and FIG. 14 and in any other suitablefilter structure. In the embodiment of FIG. 14, a fluid inlet 200communicates with the outer cylindrical surface 202 of a stack of filterdiscs 204. The fluid is filtered as it passes radially inward throughthe stack of filter discs and the filtered water passes out of thefilter via a central apertured pipe 206 and a fluid outlet 208.

Reference is now made to FIG. 15 which illustrates a filter element orfilter disc having first and second surfaces 210 and 212. In theillustrated embodiment, the first surface is formed with generallyradially disposed grooves 214 which taper as they extend inwardly fromthe surface. The second surface 212 is formed as a spacer surface,typically smooth. As seen in FIG. 16, the second surface contacts thefirst surface of an adjacent filter disc along a relatively small areaof contact therebetween. At this area of contact there are defined edgefiltering passageways extending along the grooves in contact with thesecond surface, which passageways define the minimum size of particlesseparated by the filter. The areas of contact are configured to includea circumferential band 216 and a plurality of fingers 218 extendingradially outward therefrom towards the upstream edge of the filter disc.

Fingers 218 and band 216 define a plurality of compartments 220 on theupstream side of the stack for accumulation of solid particles. It is aparticular feature of a preferred embodiment of the present inventionthat the first surface side of the compartments is formed with grooveswhich communicate with the edge filtering passageways so as to provide afluid flow path thereto even when the compartments are clogged withparticles.

FIG. 17 shows an alternative embodiment of filter discs wherein thesecond surface is not smooth but grooved in such a way that the groovesthereon cannot seat in the grooves formed on the first surface. Thisconstruction provides enhanced filtering action. It is also noted thatin the embodiment of FIG. 17, the fingers are eliminated. Thisconfiguration may be desirable in certain stack configurations whereinautomatic flushing of the stacks is provided.

FIGS. 18 and 19 illustrate filter discs having grooves 230 on a firstsurface thereof and accumulator grooves 232 formed on a second surfacethereof. The configuration of the accumulator grooves 232 is such thatcompartments 234 are defined at the upstream side of the stack forcollecting particulate matter and relatively narrow channels 236 aredefined for allowing the filtered water to reach the downstream side ofthe stack. It is noted that the slants of the grooves on the oppositesurfaces is opposite to prevent blockage of the passageways defined bythe grooves on the first surface.

Referring now to FIGS. 20 and 21, there is seen another example offilter discs having passageway defining grooves 240 on a first surfacethereof and accumulator grooves 242 on a second surface thereof. It isnoted that the second surface defines a circumferential band 244adjacent the downstream side of the filter discs which lies againstgrooves 240 to define the filter passages in addition to those passageswhich are defined between crests of adjacent accumulator grooves 242 andvalleys of passageway defining grooves.

It is noted that the groove configuration illustrated in FIGS. 20 and 21is substantially identical to that described hereinabove in connectionwith FIG. 12. Here, however, both first and second surfaces are embodiedin a single filter disc, whereas in the embodiment of FIG. 12, separatefilter discs and spacer discs were employed.

FIGS. 22, 23 and 24 illustrate filter discs having groove patterns whichcorrespond to the patterns illustrated in FIG. 12 for separate filterdiscs and spacer discs. For the sake of conciseness, the grooveconfiguration will not be repeated.

FIGS. 25, 26 and 27 illustrate filter discs having circumferentialpattern defining grooves 250 on their first surfaces and radiallyextending accumulator grooves 252 defined on their second surfaces. Itis a particular feature of this embodiment of the invention that a greatnumber of individual filter pathways are defined by the repeatedtraversals of the circumferential passageway defining grooves by theradially extending accumulator grooves 252.

FIGS. 28, 29 and 30 illustrate an alternative embodiment of accumulatorgrooves formed on a second surface of a filter disc havingcircumferential passage defining grooves formed on its first surface. Itis noted that FIG. 29 shows only the accumulator defining groove portionof the second surface of a filter disc, the remainder of the filter discbeing cut away, for purposes of illustration.

FIGS. 31 and 32 illustrate a further alternative embodiment ofaccumulator grooves formed on a second surface of a filter disc havingcircumferential passage defining grooves formed on its first surface.This configuration differs from that shown in FIGS. 28, 29 and 30 inthat it is designed for a filter configuration wherein the upstream sideis adjacent the radially outer cylindrical surface of the disc stack,while the configuration of FIGS. 28, 29 and 30 is designed for aconfiguration wherein the upstream side is adjacent the innercylindrical surface of the disc stack. It is noted that FIG. 32 showsonly the accumulator defining groove portion of the second surface of afilter disc, the remainder of the filter disc being cut away, forpurposes of illustration.

FIGS. 33 and 34 illustrate a further alternative embodiment ofaccumulator grooves formed on a second surface of a filter disc havingcircumferential passage defining grooves formed on its first surface.This configuration differs from that shown in FIGS. 28-32 in that it isdesigned for a filter configuration wherein the upstream side may beadjacent either the inner or outer cylindrical surface of the discstack. It is noted that FIG. 34 shows only the accumulator defininggroove portion of the second surface of a filter disc, the remainder ofthe filter disc being cut away, for purposes of illustration.

Reference is now made to FIG. 35 which illustrates a stack ofalternating filter discs 260 and spacer discs 262. Here, the spacerdiscs 262 are characterized in that they are formed with accumulatorgrooves 264 on their opposite sides which are tilted in oppositedirections in order to provide enhanced structural strength to thespacer discs.

FIG. 36 illustrates a high efficiency arrangement of an accumulatorgroove which may be formed on the second surface of a filter disc or ona a spacer disc. Here, The accumulator grooves extend in a back andforth circumferential orientation. The accumulator grooves arepreferably disposed against a radially grooved filter disc or radiallygrooved first surface.

Reference is now made to FIG. 37 which illustrates a filter elementhaving two additional features, both or either of which may be appliedto all of the filter element configurations described hereinabove. FIG.37 illustrates a second filter surface 300 of a filter element 301,which second filter surface 300 is shaped in sinuous configurationInstead of having relatively smooth edges as, for example, shown in theembodiments of FIGS. 3 - 11 second filter surface 300, has serratededges 302. The term "serrated" is used herein to define an edge which isnot generally smooth or straight but is conditioned so as to define anenlarged peripheral edge length and is not limited to the ordinary,possibly more limited, usual definition of the term. It is noted thatthe serrated edges are preferably arranged facing the upstream side ofthe filter stack so as to provide an enhanced edge length along whichedge filtering passageways are defined. The upstream side is indicatedby the arrow 304 which indicates the direction of water flow through thefilter stack of elements 301.

Further in accordance with an embodiment of the present invention, eachfilter element 301 is provided with one or more azimuthal positioningelements 306, typically in the form of a ring. These elements areemployed for maintaining the individual filter elements in a desiredrelative azimuthal orientation about the longitudinal axis 308 of thestack of elements. This predetermined longitudinal orientation may beimportant for providing maximum mechanical strength of the stack duringoperation at high pressures.

FIG. 38 illustrates a stack of filter elements 310 of the typeillustrated in FIG. 37 joined together in predetermined relativeazimuthal orientation by a pair of joining rods 312 which engagepositioning elements 306.

It will be appreciated by persons skilled in the art that the presentinvention is not limited by what has been particularly shown anddescribed hereinabove. Rather the scope of the invention is defined onlyby the claims which follow:

I claim:
 1. A filter, comprising: means for providing enhanced filteringcapacity for a given filter volume, including a housing having an inletconnectable to an upstream pipe, and an outlet connectable to adownstream pipe; and a stack of discs disposed within said housing forseparating solid particles from a fluid flowing between said discs fromthe upstream side of said stack to the downstream side thereof;characterized in that said stack includes:a plurality of cooperatingfilter elements defining a plurality of paired co-operating filtersurfaces, including a first surface defining a large surface area and asecond surface contacting only a portion of said large surface area ofsaid first surface and leaving a portion of the large surface area onthe upstream side of the stack not contacted thereby, at least one ofsaid first and second surfaces being formed with grooves at the areas atwhich said first and second surfaces contact, thereby to form:a)compartments on the upstream side of the stack for accumulation of solidparticles; and b) edge filtering passageways extending along the groovesin contact with said second surface, which passageways define theminimum size of particles separated by the filter and extend from saidcompartments to the downstream side of the stack, and wherein saidsecond surface is formed with serrated edge surfaces defining saidcompartments on the upstream side of the stack, thereby increasing thelength along which edge filtering passageways are defined.
 2. A filteraccording to claim 1 and wherein said first surface contains groves inthe areas of said compartments, which grooves communicate with said edgefiltering passageways for permitting liquid flow therethrough even whensaid compartments become clogged.
 3. A filter according to claim 1 andwherein said second surface contacts said first surface such that aportion of said large surface area of said first surface at thedownstream side of the stack is non-contacted by said second surface. 4.A filter according to claim 1 and wherein both said first and secondsurfaces contain grooves at the areas at which said first and secondsurfaces contact.
 5. A filter according to claim 1 and wherein saidfirst surfaces are alternated with said second surfaces.
 6. A filteraccording to claim 1 and wherein said plurality of filter elementsincludes a first plurality of filter discs interspersed with a secondplurality of spacer discs.
 7. A filter according to claim 1 and whereinsaid plurality of filter elements includes a plurality of filter discshaving said first surface formed on one face thereof and said secondsurface formed on an opposite face thereof.
 8. A filter according toclaim 1 and wherein said second surface where it contacts said firstsurface is flat.
 9. A filter according to claim 1 and wherein the areaof said first surface which is not contacted by said second surface isgreater than the area of said first surface which is contacted by saidsecond surface.
 10. A filter according to claim 1 and wherein said firstsurface has grooves extending in a generally radial direction and saidsecond surface defines upstream edges which are mostly circumferentialin orientation.
 11. A filter according to claim 10 and wherein saidmacro grooves extend generally in the radial direction and said groovesin said first surface also extend generally in the radially directionbut at a different angle than said macro grooves.
 12. A filter accordingto claim 10 and wherein said macro grooves extend generally in theradial direction and said grooves in said first surface extend in thecircumferential direction.
 13. A filter according to claim 1 and whereinsaid first surface has grooves extending in a generally circumferentialdirection and said second surface defines upstream edges which aremostly radial in orientation.
 14. A filter according to claim 1 andwherein said second surface defines edges in a sinuous configuration.15. A filter according to claim 1 and wherein said second surfacedefines macro grooves which are substantially wider than the grooves ofsaid first surface, said grooves of the first surface being contacted bythe crests of said macro grooves and being spaced from the valleys ofsaid macro grooves.
 16. A filter according to claim 1 and wherein saidgrooves in said first surface are tapered, thereby to define a fluidflow passageway in the narrowed region thereof even when the remainderthereof is filled with particles.
 17. A filter according to claim 1 andalso comprising means for maintaining said plurality of cooperatingfilter elements in a predetermined selected relative azimuthalorientation about the longitudinal axis of said stack.
 18. For use in afilter including a housing having an inlet connectable to an upstreampipe, and an outlet connectable to a downstream pipe, a filter assemblycomprising:a plurality of cooperating filter elements arranged in astack and arranged to be disposed in said housing for separating solidparticles from a fluid flowing between said elements from an upstreamside of said stack to a downstream side thereof and defining a pluralityof paired co-operating filter surfaces, including a first surfacedefining a large surface area and a second surface contacting only aportion of said large surface area of said first surface and leaving aportion of the large surface area on the upstream side of the stack notcontacted thereby, at least one of said first and second surfaces beingformed with grooves at the areas at which said first and second surfacescontact, thereby to form:a) compartments on the upstream side of thestack for accumulation of solid particles; and b) edge filteringpassageways extending along the grooves in contact with said secondsurface, which passageways define the minimum size of particlesseparated by the filter and extend from said compartments to thedownstream side of the stack, and wherein said second surface is formedwith serrated edge surfaces defining said compartments on the upstreamside of the stack, thereby increasing the length along which edgefiltering passageways are defined.
 19. For use in a filter including ahousing having an inlet connectable to an upstream pipe, and an outletconnectable to a downstream pipe, a filter assembly comprising: meansfor providing enhanced filter capacity for a given filter volume, saidmeans for providing including:a plurality of cooperating filter elementsarranged in a stack having a longitudinal axis, said plurality of filterelements defining a plurality of paired co-operating filter surfaces andmeans for maintaining said plurality of cooperating filter elements in apredetermined desired relative azimuthal orientation about thelongitudinal axis of said stack.
 20. A filter comprising:means forproviding enhanced filter capacity for a given filter volume including ahousing having an inlet connectable to an upstream pipe and an outletconnectable to a downstream pipe, and a filter assembly comprising: aplurality of cooperating filter elements arranged in a stack having alongitudinal axis, said plurality of filter elements defining aplurality of paired co-operating filter surfaces and means formaintaining said plurality of cooperating filter elements in apredetermined desired relative azimuthal orientation about thelongitudinal axis of said stack.
 21. A fluid filter comprising: meansfor providing enhanced filtering capacity includinga housing defining afluid inlet and a fluid outlet; a filter element defining an upstreamsurface communicating with the fluid inlet and a downstream generallycylindrical surface communicating with the fluid outlet, the filterelement comprising a stack of filter disks defining a hollow volumeinterior of the filter element; the stack of filter disks comprising aplurality of disks of generally annular configuration, wherein each ofat least some of said plurality of disks comprises a plurality offingers, and wherein the annular surfaces of each of at least some ofsaid plurality of disks are configured to define a raised line portionwhich in cooperation with a facing annular portion of an adjacent diskprovides filtering out of particles exceeding a predetermined size andallows fluid flowing from said fluid inlet to flow to said fluid outlet.22. A fluid filter according to claim 21 wherein each said plurality offingers is configured and arranged such that fluid flowing from saidhollow interior may come into contact with the interiors of saidfingers.
 23. A fluid filter according to claim 22 wherein substantiallyall of said pluralities of fingers each also comprise a plurality ofwebs, each individual one of said plurality of webs being disposedinteriorly of a corresponding individual one of said fingers.
 24. Afluid filter according to claim 23 wherein each individual one of saidfingers has an outline comprising first and second line portions eachextending from a tip of the finger to a base thereof and wherein eachindividual one of said plurality of webs connects at least a portion ofsaid first line portion defined by the corresponding individual one ofsaid fingers to at least a portion of said second line portion definedby the corresponding individual one of said fingers.
 25. A fluid filteraccording to claim 22 wherein substantially all of said pluralities offingers also comprises a plurality of webs, each individual ones of saidplurality of webs being disposed intermediate an individual one of saidfingers and an adjacent one of said fingers.
 26. A fluid filteraccording to claim 25 wherein each individual one of said plurality ofwebs connects at least a portion of an individual one of said fingers toat least a portion of an adjacent one of said fingers.
 27. A fluidfilter according to claim 21 wherein substantially all of saidpluralities of fingers each also comprise a plurality of webs, eachindividual one of said plurality of webs being disposed interiorly of acorresponding individual one of said fingers.
 28. A fluid filteraccording to claim 27 wherein each individual one of said fingers has anoutline comprising first and second line portions each extending from atip of the finger to a base thereof and wherein each individual one ofsaid plurality of webs connects at least a portion of said first lineportion defined by the corresponding individual one of said fingers toat least a portion of said second line portion defined by thecorresponding individual one of said fingers.
 29. A fluid filteraccording to claim 27 wherein each individual one of said fingers has anoutline comprising first and second line portions each extending from atip of the finger to a base thereof and wherein the thicknesses of saidfirst and second line portions exceeds the thickness of each of saidplurality of webs, thereby to allow fluid flowing from said hollowinterior to come into contact with said interiors of said fingers.
 30. Afluid filter according to claim 21 wherein substantially all of saidpluralities of fingers each also comprise a plurality of webs, eachindividual one of said plurality of webs being disposed intermediate anindividual one of said fingers and an adjacent one of said fingers. 31.A fluid filter according to claim 30 wherein each individual one of saidplurality of webs connects at least a portion of an individual one ofsaid fingers to at least a portion of an adjacent one of said fingers.32. A fluid filter according to claim 21 and wherein said plurality ofdisks of generally annular configuration comprises a first disk and asecond disk, each of generally annular configuration and each comprisinga said plurality of fingers, and a third disk of generally annularconfiguration sandwiched between said first and second disks.
 33. Afluid filter according to claim 21 and wherein said plurality of disksof generally annular configuration comprises first disk and a seconddisk, each of generally annular configuration, and a third disk ofgenerally annular configuration and comprising a said plurality offingers, said third disk being sandwiched between said first and seconddisks.
 34. A fluid filter according to claim 21 wherein said pluralitiesof fingers are formed on both annular surfaces of each of said at leastsome disks comprising a plurality of fingers.
 35. A fluid filteraccording to claim 21 and wherein each said raised line portion definesa plurality of grooves which, when they engage the facing annularportion of an adjacent disk, define a plurality of passages extendinggenerally from the upstream surface to the downstream surface, saidpassages being configured and arranged to allow filtering out of saidparticles and to allow the fluid flowing from said fluid inlet to flowthrough said grooves to said fluid outlet.
 36. A fluid filter accordingto claim 21 and wherein at least some of the individual ones of saidplurality of disks which do not comprise a plurality of fingers haveformed thereon a plurality of generally circumferential passages.
 37. Afluid filter according to claim 36 and wherein at least some of saiddisks formed with said plurality of fingers have formed thereon at leastone generally circumferentially extending groove defining a plurality ofgenerally circumferential passages.
 38. A fluid filter according toclaim 37 and wherein said at least one generally circumferentiallyextending groove comprises a plurality of generally circumferentialgrooves.
 39. A fluid filter according to claim 21 and wherein generallythe entirety of said plurality of disks is arranged such that only everyother disk comprises a plurality of fingers.
 40. A fluid filteraccording to claim 21 and wherein said stack of filter disks comprises aplurality of disk pairs comprising first and second adjacent disks, eachsaid first disk having a surface thereof facing a surface of theadjacent second disk, said facing surface on each said first disk beingformed with a plurality of first grooves, said facing surface on eachsaid second disk being formed with a plurality of second grooves, eachsaid first groove on an individual first disk intersecting at least onesaid second groove on the adjacent second disk.
 41. A filter accordingto claim 21 and wherein at least a portion of the raised line portionhas a serrated configuration and at least some of the filter disks ofsaid stack define a filter barrier between the upstream side of thestack and the downstream side of the stack, said barrier being definedby a plurality of grooves, at least some of said plurality of groovesbeing defined by the serrated configuration of at least the portion ofthe raised line pattern.